# `Expresso.SignalHandler`
[🔗](https://github.com/rellen/expresso/blob/main/lib/expresso/signal_handler.ex#L1)

The handler of the signals of the operating system in the binary

The default handler of OTP stops the VM in order for a SIGTERM. That stop
waits for each application to stop, and the command of the binary runs in
`Expresso.BurritoEntryPoint.start/2`, before the application starts. The
stop then waits for ever, and the logger writes to the standard output while
it waits.

The launcher of Burrito 1.6 sends SIGTERM when the reader of the standard
output stops, as `| head` does. The launcher passes the standard output of
the VM through a pipe, and it stops the read of that pipe first. Thus each
write to the standard output also waits for ever, and the binary did not
stop. See `stdoutCopyThread` in `deps/burrito/src/erlang_launcher.zig`.

This handler halts the VM at once for a SIGTERM, and it does not write to the
standard output. The default handler of OTP handles the other signals.

The launcher does not send on a SIGTERM that the user sends to the binary.
`Expresso.LauncherWatch` halts the VM when the launcher stops.

The exit status is 0. The launcher waits for the VM in two threads, and the
thread that reads the exit status first decides the status of the binary.
When the thread that sent SIGTERM reads it first, the binary gives 0 for each
status of the VM. A different status of the VM then gives 0 or that status
by chance. With 0, a closed pipe always gives 0, as `mix expresso` does.

# `install`

```elixir
@spec install() :: :ok | {:error, term()}
```

Replace the default handler of OTP with this handler

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*Consult [api-reference.md](api-reference.md) for complete listing*